Oxygen interaction with Si(100) and K/Si(100)

The earliest stages of the oxygen interaction with clean and K-covered Si(100) surfaces (Theta(K) less than or equal to 0.5 ML) have been investigated using high-resolution core-level photoemission. The sequence of oxidation has been analyzed monitoring the different components of the Si 2p core level. In the case of the clean surface, the contribution coming from the upper dimer atoms is unaffected at the earliest stages of the oxidation. On the contrary, in the presence of It atoms, oxygen reacts rapidly with this type of silicon atoms, and the component is fully depleted after oxygen adsorption. The presence of I; atoms induces also the formation of a new oxide component in the Si 2p core level. Its small binding energy shift supports that a fraction of oxygen atoms are bonded at sites modified by the presence of K, forming a K-Si-O complex.